Chemistry: Acids, Bases, Electrolysis, and Transition Metals

What defines an acid in aqueous solution?

An acid is a substance that produces hydrogen ions in aqueous solution

How is a chemical base defined?

A base is a substance that accepts H^+ ions and neutralises an acid.

What defines an acid in aqueous solution?

An acid is a substance that produces H^+ ions in aqueous solution.

How is a chemical base defined?

A base is a substance that accepts H^+ ions and neutralises an acid.

What is the distinction between a base and an alkali?

An alkali is a base that is soluble in water and produces OH}^- ions.

What are the general products of a reaction between a metal oxide and an acid?

A salt and water.

What is the balanced equation for the neutralisation of hydrochloric acid by magnesium oxide?

MgO_2+2HCl →Mg〖Cl〗_2+2H_2 O

What product forms when sodium oxide reacts with water?

Sodium hydroxide

Which ion is directly responsible for making a solution alkaline?

The hydroxide ion

What is the fundamental ionic equation representing neutralisation between an acid and an alkali?

H^(+ )+OH^- → H_2 O

Why is magnesium hydroxide useful as an antacid?

Its basic nature allows it to neutralise excess stomach acid (hydrochloric acid).

How does magnesium oxide help preserve paper in old books?

Its basic nature neutralises acidic substances present in the paper.

What chemical name and formula describe quicklime after it reacts exothermically with water?

Calcium hydroxide (Ca〖(OH)〗_2), also known as slaked lime.

Why do farmers treat acidic soil with calcium hydroxide?

Calcium hydroxide neutralises soil acidity, raising the pH for optimal crop growth.

What is saponification?

The reaction of sodium hydroxide with fats and oils to produce soap and glycerol.

What is the balanced equation for the neutralisation of sulfuric acid effluent using calcium hydroxide?

Ca〖(OH)〗_2+H_2 SO_4 →CaSO_4+2H_2 O

Concept: Amphoteric substance

Definition: A substance capable of reacting as both an acid and a base. Example: Aluminium oxide 〖Al〗_2 O_3

What is the balanced equation for aluminium oxide reacting with hydrochloric acid?

〖Al〗_2 O_3+6HCl →2Al〖Cl〗_3+3H_2 O

What balanced equation represents aluminium oxide behaving as an acid with aqueous sodium hydroxide?

〖Al〗_2 O_3+2NaOH+3H_2 O →2Na[Al(OH)_2]

What product is formed when aluminium oxide reacts with hot, concentrated sodium hydroxide?

Sodium tetrahydroxoaluminate (2Na[Al(OH)_2]).

Why does observing aluminium oxide react with an acid not prove it is amphoteric?

Reaction with an acid proves basic behavior only; reaction with a base must also be demonstrated.

Term: Electrolysis

Definition: The chemical decomposition of a substance using a direct electric current.

Why do ionic compounds conduct electricity when molten or dissolved, but not when solid?

In the solid state ions are fixed in a lattice, whereas in molten or aqueous states ions are mobile to carry charge.

What particles carry electric current in the external circuit versus the electrolyte during electrolysis?

Electrons carry charge in the external wires, whereas mobile ions carry charge through the electrolyte.

Term: Cathode

Definition: The negative electrode during electrolysis, which attracts positive cations.

Term: Anode

Definition: The positive electrode during electrolysis, which attracts negative anions.

What type of chemical reaction occurs at the cathode during electrolysis?

Reduction, which involves the gain of electrons.

What type of chemical reaction occurs at the anode during electrolysis?

Oxidation, which involves the loss of electrons.

What is the half-equation for the reduction of sodium ions in the electrolysis of molten sodium chloride?

〖Na〗^+ + e^- →Na

What is the half-equation for the oxidation of chloride ions in the electrolysis of molten sodium chloride?

2〖Cl〗^- → 〖Cl〗_2 (g)+2e^-

What is the overall balanced equation for the electrolysis of molten sodium chloride?

2NaCl →2Na+〖Cl〗_2

What half-equation occurs at the cathode during the electrolysis of molten magnesium chloride?

〖Mg〗^(2+)+2e^-→Mg

What half-equation occurs at the anode during the electrolysis of molten magnesium chloride?

2〖Cl〗^- → 〖Cl〗_2 (g)+2e^-

What standard electrode potential value (E°) is assigned to the standard hydrogen electrode?

0.00 V

In aqueous electrolysis, how does a species' (E°) value affect its reduction tendency at the cathode?

A species with a more positive (E°) value has a greater tendency to gain electrons and undergo reduction.

What product forms at the cathode during the electrolysis of concentrated aqueous sodium chloride (brine)?

Hydrogen gas

What product forms at the anode during the electrolysis of concentrated aqueous sodium chloride (brine)?

Chlorine gas

Why does aqueous sodium chloride produce hydrogen at the cathode instead of sodium metal?

Water is reduced more readily than sodium ions under aqueous conditions.

What anode product is primarily formed during the electrolysis of dilute sodium chloride solution?

Oxygen gas

What products are formed at the cathode and anode during the electrolysis of aqueous copper(II) sulfate with inert electrodes?

Copper metal forms at the cathode and oxygen gas forms at the anode.

What products are formed at the cathode and anode during the electrolysis of aqueous copper(II) chloride?

Copper metal forms at the cathode and chlorine gas forms at the anode.

What products are formed at the cathode and anode during the electrolysis of aqueous sodium sulfate?

Hydrogen gas forms at the cathode and oxygen gas forms at the anode.

Term: Transition metal

Definition: An element that forms at least one stable ion with a partially filled d-subshell.

How do transition metals compare to Group 1 metals regarding density and melting points?

Transition metals generally have significantly higher densities and higher melting points.

How do transition metals compare to Group 1 metals regarding reactivity with water?

Transition metals react slowly or not at all with water, whereas Group 1 metals react vigorously.

Which three transition metals exhibit ferromagnetic properties?

Iron (Fe), Cobalt (Co), and Nickel (Ni).

Why do transition metals exhibit variable oxidation states?

Their 3d and 4s electron subshells have very similar energy levels.

What information does the Roman numeral provide in transition-metal compound names?

The Roman numeral specifies the oxidation state (or ionic charge) of the transition metal.

What is the chemical formula for iron(III) chloride?

FeCl_3

What is the chemical formula for manganese(IV) oxide?

MnO_2

Why are transition-metal complex compounds frequently coloured?

Partially filled d-orbitals split into different energy levels, allowing electrons to absorb specific wavelengths of visible light.

Term: Ligand

Definition: An ion or molecule that donates a lone pair of electrons to a central metal ion.

Term: Dative covalent bond

Definition: A covalent bond in which both shared electrons originate from the same atom or ion.

Term: Coordination number

Definition: The total number of dative covalent bonds formed between ligands and a central metal ion.

What is the central ion, coordination number, and overall charge of [Fe(H₂O)₆]²⁺?

The central ion is Fe²⁺, the coordination number is 6, and the overall charge is 2+.

What is the central ion and ligand in the complex ion [CuCl₄]²⁻?

The central metal ion is Cu²⁺ and the ligands are chloride ions Cl⁻.

How do transition-metal catalysts lower the activation energy of a chemical reaction?

They provide an alternative reaction pathway by changing oxidation states or adsorbing reactants onto their surfaces.

What reaction is catalysed by platinum, palladium, and rhodium in catalytic converters?

2CO(g) + 2NO(g) → 2CO₂(g) + N₂(g)

Which catalyst is used in the Contact process for the industrial production of sulfuric acid?

Vanadium(V) oxide (V₂O₅).

Which transition metal is used as the catalyst in the Haber process for manufacturing ammonia?

Iron (Fe).